The field of the invention is telecommunications systems and particularly telecommunications circuitry which eliminates the need of directly connecting display terminals to a controller with coaxial cable.
Standard multi-terminal computer installations utilize coaxial cable or coax between each terminal on the system and the controller for that terminal. Coaxial cable is very expensive and, if it is to be pulled through raceways, causes additional expense during installation.
Developments in the past have recognized this problem and a number of systems have been achieved to reduce the requirement for coaxial cable in a multi-terminal configuration. These have included the use of a single coaxial cable of up to five thousand feet in length which, when connected to an interface circuit, can operate up to eight terminals. Past developments have also included a four wire, two pair connection between two interfacing circuits with transmission in both directions, one direction on each pair of twisted wire. While the four wire, two pair system enables the transmission of data over longer distances and is substantially cheaper to install than coaxial cable, transmission on a single pair enables the cost of installation or operation of the system to be halved. With a single pair only one leased line need be rented from the local telephone company or the cost of installation is reduced to that necessary for a single pair.